Method and apparatus for controlling flow of well fluids



Sept. 28, 1965 J. H. BAYLESS 3,208,527

METHOD AND APPARATUS FOR CONTROLLING FLOW OF WELL FLUIDS Filed July 10, 1961 2 Sheets-Sheet 1 IINVENTOR.

I JACK H. BAYLESS, 48 12W ATTORNEY.

FIG.

Sept. 28, 1965 J. H. BAYLESS 3,208,527

METHOD AND APPARATUS FOR CONTROLLING FLOW OF WELL FLUIDS Filed July 10. 1961 2 Sheets-Sheet 2 g is? INVENTOR.

JACK H. BAYLESS,

ATTORNEY.

United States Patent 3,208,527 METHOD AND APPARATUS FOR CONTROLLING FLGW 0F WELL FLUIDS Jack H. Bayiess, Houston, Tex., assignor, by mesne assignments, to Esso Production Research Company, Houston, Tex., a corporation of Delaware Filed July 10, 1961, Ser. No. 122,768 Claims. (Cl. 166-39) The present invention relates to an assembly of downhole equipment designed for use with :a multiple-phase cyclic in-situ well stimulation technique in which each cycle consists of injection of air into and production of oil from the same well with constant temperature monitoring.

In the stimulation of wells by in-situ combustion techniques, it is costly and time consuming and consequently quite undesirable to work over the well for each phase of the stimulation cycle. In the past, in this type of operation is has been necessary to initially work over the well in order to install a thermowell, injection and production strings, and then work over the well again when installing a pump. These procedures caused the loss of temperature measuring equipment and damage to production capacity, and further, subsequent stimulation required still another workover.

A primary object of the invention described herein is to avoid working over the well for each phase of the in-situ combustion stimulation cycle and to permit complete freedom in the many required operations. Only the intial workover is required when the arrangement of well equipment in accordance with the invention is employed.

The well assembly apparatus for use with the multiple phase cyclic in-situ combustion subsurface formation stimulation technique comprises two spaced-apart pipe strings extending from the earths surface downwardly in a well bore; a packer arranged in the well bore closing off the space between said pipe strings and the wall of the well bore; a first valve arranged in one of said pipe strings above the packer and movable between one position which establishes a first flow path between the surface of the earth and the formation isolated from the space surrounding said pipe strings above the packer and extending through the packer, the first valve, and said one pipe string; and another position which prevents fluid communication between the formation and the earths surface through said packer and said first valve but which also establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve and said one pipe string; means lowerable through said one pipe string for moving said first valve between its two positions; at least one second valve arranged in said other pipe string above said first valve and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which establishes a third flow path between said formation and the space surrounding said pipe strings above said packer through said other pipe string and said second valve; and means lowerable through the other pipe string for moving said second valve between its two positions. A pump is lowerable through said one pipe string to adjacent said first valve and the pump also may be used as the means for moving the first valve between its two positions. Also, a thermocouple is lowerable through the other string to a position adjacent the formation for supplying temperature indications to the earths surface. The thermocouple may be provided with electromagnetic valve operating means which may be used as the means for moving the second valve between its two positions. The operation is as follows: with the first 3,28,5Z7 Patented Sept. 28, 1965 valve in its one position, air is injected from the earths surface into the formation along the first flow path to initiate and maintain in-situ combustion for a desired period of time. Injection of air is halted when it is desired to terminate the combustion phase, and following completion of the combustion phase, oil is produced from the formation to the earths surface also along the first flow path until production ceases. Then the pump is lowered through the one pipe string, and the first valve is moved to its other position to establish the second flow path through the first valve and the pump and the one pipe string. The second valve at this time is in its other position, which establishes the third flow path. Hydrocarbons are produced from the formation through the other pipe string to the second valve, at which point gas separates from oil. The gas passes upwardly through the space between the pipe strings and the well bore wall to the earths surface, and the oil passes from the third flow path into the second fiow path to the earths surface. Temperature readings may be taken by means of the thermocouple at any time during the cycle of operations. A third valve may be provided in the other pipe string below the packer. This third valve is movable in the same way the second valve is movable between one position which prevents fluid communication between the interior of the other pipe string and the space surrounding it and another position which permits such communication. This valve is used to provide access to the interior of the other pipe string for production through the third and second flow paths, as described supra. In this arrangement, a one-way check valve is positioned on the lower end of the other pipe string and functions to prevent well fiuid from entering the other pipe string when injecting fluids such as corrosion inhibitors into the well bore through the other pipe string.

The above and other objects and advantages of the invention will be apparent from a more detailed description thereof taken in conjunction with the drawings in which:

FIGS. 1, 2, and 3 schematically show a cross section of the earths surface penetrated by a well bore in which is arranged dual pipe strings, a thermowell, and other equipment for carrying out the method of operation of the invention, which is illustrated in stages in these figures;

FIG. 4 is a cross-sectional view of a portion of the injection-production tubing showing its sliding sleeve valve arranged in closed position;

FIG. 5 is a cross-sectional view of a portion of the thermowell-separator tubing showing one of its sleeve valves in closed position; and

FIG. 6 is a cross-sectional view of the thermocouple showing details of the valve locking mechanism.

Referring to the drawings in greater detail, in FIGS. 1 to 3 there is shown a casing pipe string 10 penetrating a subsurface producing formation 11. Perforations 12 are formed in pipe string 10 adjacent formation 11. A dual-bore packer 13 is positioned in pipe string 10 above formation 11. An injection-production pipe string 14 terminates in one of the bores of packer 13. A sliding sleeve valve A is connected into pipe string 14 adjacent packer 13.

The details of valve A, which consists of a coupling 15 screw threaded to pipe string 14 and a sleeve 16 vertically slidable in it, are shown in FIG. 4; and as seen therein, coupling 15 is provided with ports 17 adjacent the upper end thereof, a recess 18 formed on the interior surface thereof, in which is arranged a snap ring 19, an enlarged interior area portion 20, a sealing surface 21, and a seating surface 22 adjacent the lower end thereof. Sleeve 15 is provided at its upper end with a pumplanding recess 25 formed to engage and land the bottom of a pump barrel and ports 26 formed below the pumplanding recess. These ports align with ports 17 in coupling 15 when sleeve 16 is in its lower position (not shown). Seals 27, 28, and 29 are provided onthe outer surface of sleeve 16. Also provided on the outer surface are indents 30 and 31. Lower ports 32 are formed in sleeve 16, and the lower end thereof is beveled to form a seat 33.

Referring again to FIGS. 1 to 3, a thermowell separator string 35 is arranged in pipe string and extends through packer 13. The lower part of tubing string 35 below packer 13 forms a thermowell 47. Optionally, a check valve 48 may be positioned on the lower open end of pipe string 35. When running the equipment into pipe string 10 preferably dual bore packer 13 with the thermowell 47 portion of tubing string 35 attached to it is lowered and set such that the valve B is positioned at a desired location above formation 11. Then the upper portion of tubing 35 and tubing 14 can be run and lodged in packer 13 with valves C and A suitably positioned; or if desired, the entire tubing 35 can be run into the well with packer 13 separate from or together with the running of tubing 14. These techniques are conventional practice, and the equipment for accomplishing them is commercially available.

Pipe string 35 is provided with at least two sleeve valves B and C, one of which B is located below packer 13. Each valve includes, as seen in detail in FIG. 5, a coupling or collar 36 screw threaded to pipe string 35, within which vertically slides a sleeve 37. Coupling 36 is provided with ports 38 and also on the interior surface thereof with an indent 39 in which is arranged a snap ring 40. Sleeve 37 is provided with ports 41 which, when sleeve 37 is in its lower position, align with ports 38. Also, sleeve 37 is provided with indents or grooves 42 and 43 and seals 44 and 45 on the outer surface thereof and an engaging ring 46 on the interior surface thereof.

As seen in FIGS. 2 and 3, a thermocouple 50 is suspended in tubing string 35 on an electrically conductive cable 51. The details of the electromagnetic portion of the thermocouple head are shown in FIG. 6. The thermocouple head forms a housing 55 in which is arranged a plunger 56 biased upwardly by means of a spring 57 and surrounded by copper coils 58, which are electrically connected to a source of energy at the surface through one of the leads or conductors 59 of cable 51. The lower end 60 of plunger 56 is tapered, and this end contacts a plurality of latches 61 provided with tapered surfaces 62, which engage the tapered surface of plunger 56. Latches 61 are spring biased inwardly by bow springs 63, and the latches when extended protrude through openings 64 in housing 55. Leads 65 and 66, one constantan and one copper, connect to the thermocouple element 67 through housing 55.

To illustrate the operation and the utility of the invention, a complete stimulation cycle now will be described. In the in-situ combustion step (FIG. 1), air is injected through tubing string 14 into formation 11 through perforations 12 (the path of air flow is designated by the arrows), and during this phase of a cycle, the sliding sleeve valve A of tubing 14 and valves B and C in the separator thermocouple tubing 35 are in the positions shown in FIGS. 4 and 5, respectively. In this position of valve A, snap ring 19 fits into indent 31 and retains sliding sleeve 16 in its upper position; seals 27 and 28, which may be suitably O-ring seals, seal off and isolate ports 17; and in this position of valve B or C, snap ring 40 fits into indent 39 and retains sleeve 37 in the upper position and seals 44 and 45, which may be O-ring seals, seal off openings 38 in coupling 36.

When the air injection phase is terminated, the well is placed on production on a flowing basis, which lasts for several days to several weeks. In this phase, well fluids are produced through perforations 12 in pipe string 10 and upwardly through tubing string 14 (the path of flow of production fluid is designated by the arrows), as seen in FIG. 2. Valves A and B, C remain in the positions shown in FIGS. 4 and 5, respectively.

When the well finally stops flowing, the pump barrel 70 is lowered on the sucker rod string 71 through production tubing string 14 and, as seen in FIG. 3, is landed in the pump-landing recess 25 of sleeve 16. Sleeve 16 is moved downwardly by the pump until surface 33 engages surface 22 (see FIG. 4). In this position, seal 29 seals off against surface 21 to thereby seal off fluid flow through ports 32. Also, indent 30 engages snap ring 19 to latch sleeve 16 in its lowermost position, and seal 27 is positioned then below ports 17; and ports 26 and 17 are aligned and in fluid communication. The lower end of the pump barrel is firmly latched to sleeve 16.

Oil production in this type stimulation is very gassy, and consequently inefficient pumping results. Therefore, after the pump is set, the lowermost sliding sleeve valve B in the thermowell portion of tubing 35 is opened by the electromagnetic latch in the thermocouple head energized by current in the two copper leads 59 and 65. Thus, by moving plunger 56 downwardly against the bias of spring 57 by energizing coil 58, surface 60 urges latches 61 outwardly against the bias of springs 63 and engages the topside of rings 46; the weight of the tool or downward jarring unlatches snap ring 39 and moves sleeve 37 downwardly until ports 41 and 38 are aligned. In this position, O-ring 45 is below opening 38. An indent 42 latches sleeve 37 in its lowermost position. As seen in FIG. 3, lower sleeve valve B is open. Then, one of the upper sleeve valves C is opened in a similar manner, as illustrated, to allow production to rise through the thermowell to any of the preset heights. If desired, sleeve valves B and C may be opened by wire line equipment other than the thermocouple. The gas in the production fluids passes upwardly through the casing annulus, while the oil flows downwardly and collects above packer 13 and is picked up by pump 70. The height of the gas-oil separator can be adjusted by opening and closing different sliding sleeve valves C.

It is seen that temperature surveys with the wire line thermocouple may be made at any time in the cycle. In another air injection cycle, all sliding sleeves in tubing 35 can be closed and pump 70 in tubing 14 unseated, raising sleeve 16 of valve A to its position in FIG. 4 to allow injection of air down tubing 14. Although it is preferable, as described, to inject the air through tubing string 14, if desired air may be injected through tubing string 35 instead.

The optional check valve 48 at the bottom of the thermowell may be used to permit injection of corrosion inhibitor during the initial flowback if that is desired or to permit the alternate operation of air injection through tubing 35.

Having fully described the apparatus, objects, method of operation, and nature of my invention, 1 claim:

1. A well assembly for use with a multiple phase cyclic in situ combustion subsurface formation stimulation technique comprising:

two spaced-apart pipe strings extending from the earths surface downwardly in a well bore;

a packer arranged in said well bore above said formation and closing oft" the space between said pipe strings and the wall of said well bore;

first valve means arranged in one of said pipe strings above said packer and movable between one position which establishes a first flow path between the surface of the earth and said formation isolated from the space surrounding said pipe strings above the packer and extending through said packer, said first valve means and said one pipe string, and another position which prevents fluid communication between said formation and the earths surface through said packer and said first valve means, but which establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve means and said one pipe string;

means lowerable through said one pipe string for moving said first valve means from its one position to its other position and vice versa;

at least one second valve means arranged in said other pipe string above said first valve means and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which establishes -a third flow path between said formation and the space surrounding said pipe string above said packer through said other pipe string and said second valve means; and

means lowerable through said other pipe string to a position adjacent said formation for moving said second valve means from its one to its other position and vice versa;

whereby when said first valve means is in its one position, air may be injected from the earths surface into said formation along said first flow path to ini tiate and maintain in situ combustion for a selected time, after which injection of air may be terminated to complete the combustion phase, and following completion of the combustion phase, oil may be produced from said formation to the earths surface also along said first flow path until production thereof ceases; then said first valve means may be moved to its other position to establish said second flow path through said first valve means and said one pipe string, said second valve means being in its other position to establish said third flow path and oil may then be pumped to the earths surface from adjacent said first valve means, said hydrocarbons produced from said formation flowing upwardly therefrom through said third flow path into the space surrounding said pipe strings above said packer where gas separates from oil, the gas flowing upwardly through the annulus between said other pipe string and the well bore wall to the earths surface and oil flowing from said third flow path into said second flow path and, thence, upwardly to the earths surface.

2. A well assembly as recited in claim 1 wherein said means lowerable through said one pipe string for moving said first valve means to its different positions includes a pump used to pump oil to the earths surface during the pumping phase of the cycle and said means for moving said second valve means to its diiferent positions includes a thermocouple having an electromagnetic valve operating means arranged therein, said thermocouple providing temperature readings at any desired time.

3. A well assembly as recited in claim 1 wherein said means for moving said second valve means to its different positions comprises a combination thermocouple and valve operating means for measuring temperatures in the well and for use in manipulating movable well pipe valve elements which comprises:

a thermocouple element;

valve operating means attached to said thermocouple element and including a spring-biased plunger; electrical means for moving said plunger against the bias of said spring;

latch means engaging said plunger and adapted to move outwardly on movement of said plunger against the bias of said spring to engage said second valve means for operation thereof;

biasing means adapted to urge said latch means inwardly out of engagement with said second valve means; and

an electrical conductor cable connected to said thermocouple element and to said electrical means for suspending said thermocouple element and valve operating means in a well and for transmitting tem- 4. A well assembly for use with a multiple phase cyclic 5 in situ combustion subsurface formation stimulation technique comprising:

two spaced-apart pipe strings extending from the earths surface downwardly in a well bore;

a packer arranged in said well bore above said formation and closing off the space between said pipe strings and the wall of said well bore;

first valve means arranged in one of said pipe strings above said packer and movable between one position which establishes a first flow path between the surface of the earth and said formation isolated from the space surrounding said pipe strings above said packer and extending through said packer, said first valve means and said one pipe string, and another position which prevents fluid communication between said formation and the earths surface through said packer and said first valve means, but which establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve means and said one pipe string;

means lowerable through said one pipe string for moving said first valve means from its one position to its other position and vice versa;

at least one second valve means arranged in said other pipe string above said first valve means and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which permits fluid communication between the interior of said other pipe string and the space surrounding it;

third valve means arranged in said other pipe string means lowerable through said other pipe string for moving said second and third valve means between the two positions of each;

whereby when said first valve means is in its one position air may be injected from the earths surface into said formation along said first flow path to initiate and maintain in situ combustion for a selected time, after which injection of air may be terminated to complete the combustion phase and following completion of the combustion phase, oil may be produced from said formation to the earths surface also along said first flow path until production thereof ceases; then said first valve means may be moved to its other position to establish said second flow path through said first valve means and said one pipe string, said second valve means and said third valve means being in their other positions to establish said third flow path and oil may then be pumped to the earths surface from adjacent said first valve means, said hydrocarbons produced from said formation flowing upwardly therefrom through said third flow path into the space surrounding said pipe strings above said packer where gas separates from oil, the gas flowing upwardly from the annulus between said other pipe string and the well bore wall to the earths surface and oil flowing from said third flow path into said second flow path and, thence, upwardly to the earths surface.

5. A well assembly as recited in claim 4 wherein said means lowerable through said one pipe string for moving said first valve means to its different positions includes a pump for pumping oil to the earths surface during the pumping phase of the cycle and said means for moving said second valve means and said third valve means to the different positions of each comprising a thermocouple having an electromagnetic valve operating means arranged therein, said thermocouple providing temperature readings at any desired time.

6. A well assembly as recited in claim including a oneway valve arranged on the lower end of said other pipe string adapted to permit fluidto flow from the interior of said other pipe string and prevent fluid flow to the interior of said other pipe string.

7. A well assembly comprising:

two spaced-apart pipe strings extending from the earths surface downwardly in a well bore;

a packer arranged in said well bore above a subsurface formation and closing off the space between said pipe strings and the wall of said well bore;

first valve means arranged in one of said pipe strings above said packer and movable between one position which establishes a first flow path between the surface of the earth and said formation isolated from the space surrounding said pipe strings above the packer and extending through said packer, said first valve means and said one pipe string, and another position which prevents fluid communication between said formation and the earths surface through said packer and said first valve means but which establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve means and said one pipe string;

means including a pump adapted to pump oil to the earths surface, lowerable through said one pipe string for moving said first valve means from its one position to its other position and vice versa;

at least one second valve means arranged in said other pipe string above said first valve means and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which establishes a third flow path between said formation and the space surrounding said pipe strings above said packer through said other pipe string and said second valve means; and

means including a thermocouple having an electromagnetic valve operating means arranged therein lowerable through said other pipe string to a position adjacent said formation for moving said second valve means from its one to its other position and vice versa;

whereby positioning of said first and second valve means in a selected manner controls flow of fluids between the earths surface and said formation while said thermocouple provides temperature readings at any desired time.

8, A well assembly comprising:

two spaced-apart pipe strings extending from the earths surface downwardly in a well bore;

a packer arranged in said well bore above a subsurface formation and closing off the space between said p1pe strings and the wall of said well bore;

first valve means arranged in one of said pipe strings above said packer and movable between one position which establishes a first flow path between the surface of the earth and said formation isolated from the space surrounding said pipe strings above said packer and extending through said packer, said first valve means and said one pipe string, and another position which prevents fluid communication between said formation and the earths surface through said packer and said first valve means but which establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve means and said one pipe string;

means including a pump adapted to pump oil to the earths surface, lowerable through said one pipe string for moving said first valve means from its one position to its other position and vice versa;

at least one second valve means arranged in said other pipe string above said first valve means and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which permits fluid communication between the in terior of said other pipe string and the space sur rounding it;

third valve means arranged in said other pipe string below said packer and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which in cooperation with said second valve means and said other pipe string between said second and third valve means establishes a third flow path between said formation and the space surrounding said pipe strings above said packer; and

means including a thermocouple having an electromagnetic valve operating means arranged therein lowerable through said other pipe string for moving said second and third valve means to the different positions of each;

whereby positioning of said first, second, and third valve means in a selected manner controls flow of fluids between the earths surface and said formation while said thermocouple provides temperature readings at any desired time.

9. In a multiple phase cyclic in situ combustion subsurface formation stimulation method utilizing two spaced-apart pipe strings extending from the earths surface downwardly in a well bore; a packer arranged in said well bore above said subsurface formation and closing off the space between said pipe strings and the wall of said well bore; first valve means arranged in one of said pipe strings above said packer and movable between one position which establishes a first flow path between the surface of the earth and said formation isolated from the space surrounding said pipe strings above the P cker and extending through said packer, said first valve means and said one pipe string, and another position which prevents fluid communication between said formation and the earths surface through said packer and said first valve means but which establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve means and said one pipe string; means lowerable through said one pipe string for moving said first valve means from its one position to its other position and vice versa; at least one second valve means arranged in said other pipe string above said first valve means and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which establishes a third flow path between said formation and the space surrounding said pipe strings above said packer through said other pipe string and said second valve means; and means lowerable through said other pipe string to a position adjacent said formation for moving said second valve means from its one to its other position and vice versa, the steps comprising:

positioning said first valve means in its one position;

injecting air from the earths surface into said formation along said first flow path to initiate and maintain in situ combustion for a selected time;

terminating said injection of air after said selected time to complete the combustion phase;

producing oil from said formation to the earths surface along said first flow path until production ceases; positioning said first valve means in its other position to establish said second flow path;

positioning said second valve means in its other position to establish said third flow path; and

pumping oil to the earths surface from adjacent said first valve means, said hydrocarbons produced from said formation flowing upwardly therefrom through said third flow path into the space surrounding said pipe strings above said packer where gas separates from oil, the gas flowing upwardly through the annulus between said other pipe string and the well bore wall to the earths surface and the oil flowing from said third flow path into said second flow path and, thence, upwardly to the earths surface.

10. In a multiple phase cyclic in situ combustion subsurface formation stimulation method utilizing two spaced-apart pipe strings extending from the earths surface downwardly in a Well bore; a packer arranged in said well bore above said formation and closing off the space between said pipe strings and the Wall of said well bore; first valve means arranged in one of said pipe strings above said packer and movable between one position which establishes a first flow path between the surface of the earth and said formation isolated from the space surrounding said pipe strings above said packer and extending through said packer, said first valve means and said one pipe string, and another position which prevents fluid communication between said formation and the earths surface through said packer and said first valve means, but which establishes a second flow path between the earths surface and the space surrounding said pipe strings above said packer through said first valve means and said one pipe string; means lowerable through said one pipe string for moving said first valve means from its one position to its other position and vice versa; at least one second valve means arranged in said other pipe string above said first valve means and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which permits fluid communication between the interior of said other pipe string and the space surrounding it; third valve means arranged in said other pipe string below said packer and movable between one position which prevents fluid communication between the interior of said other pipe string and the space surrounding it and another position which in cooperation with said second valve means and said other pipe string between said second and third valve means establishes a third flow path between said formation and the space surrounding said pipe strings above said packer; and means lowerable through said other pipe string for moving said second and third valve means to the positions of each, the steps comprising:

positioning said first valve means in its one position;

injecting air from the earths surface into said formation along said first flow path to initiate and maintain in situ combustion for a selected time;

terminating injection of air after said selected time to complete the combustion phase;

producing oil upon completion of the combustion phase from said formation to the earths surface along said first flow path until production ceases;

positioning said first valve means in its other position to establish said second flow path;

positioning said second valve means and said third valve means in their other positions to establish said third flow path; and

pumping oil to the earths surface from adjacent said first valve means; said hydrocarbons produced from said formation flowing upwardly therefrom through said third flow path into the space surrounding said pipe string above said packer where gas separates from oil, the gas flowing upwardly from the annulus between said other pipe string and the well bore wall to the earths surface and the oil flowing from said third flow path into said second flow path and, thence, upwardly to the earths surface.

References Cited by the Examiner UNITED STATES PATENTS 1,202,319 10/16 Robinson 166-189 1,374,833 4/ 21 Dooley 294-88 1,374,834 4/21 Dooley 294-88 1,674,815 6/28 Barnhart 103-203 2,196,664 4/40 Kofahl 137-62548 2,3 04,303 12/42 Ferguson 137-62517 2,311,212 2/43 Coberly 137-62549 2,444,754 7/48 Steffen 166-62 2,567,513 9/51 Haines 166-62 2,719,485 10/55 Bendor 294-88 2,819,761 1/58 Popham et al 166-39 2,906,340 9/59 Herzog 166-39 2,958,380 11/60 Schild 166-11 3,000,441 9/ 61 Kunetka 166-39 3,044,546 7/62 Dixon 166-11 3,047,064 7/62 West et al. 166-11 -3 ,05 0, 1 21 8 62 Garrett 166-45 3,126,955 3/64 Tranthan 166-11 3,115,187 12/64 Brown 166-224 OTHER REFERENCES Garrett, H. U.: Parallel Macaroni String Cuts Well Costs. The Petroleum Engineer, January 1957, vol. 29, No. 1, pp. B38, 4044. TN 860 P4.

BENJAMIN HERSH, Primary Examiner. CHARLES E. OCONNELL, Examiner. 

9. IN A MULTIPLE PHASE CYCLIC IN SITU COMBUSTION SUBSURFACE FORMATION STIMULATION METHOD UTILIZING TWO SPACED-APART PIPE STRINGS EXTENDING FROM THE EARTH''S SURFACE DOWNWARDLY IN A WELL BORE; A PACKER ARRANGED IN SAID WELL BORE ABOVE SAID SUBSURFACE FORMATION AND CLOSING OFF THE SPACE BETWEEN SAID PIPE STRINGS AND THE WALL OF SAID WELL BORE; FIRST VALVE MEANS ARRANGED IN ONE OF SAID PIPE STRINGS ABOVE SAID PACKER AND MOVABLE BETWEEN ONE POSITIOP WHICH ESTABLISHERS A FIRST FLOW PATH BETWEEN THE SURFACE OF THE EARTH AND SAID FORMATION ISOLATED FROM THE SPACE SURROUNDING SAID PIPE STRINGS ABOVE THE PICKER AND EXTENDING THROUGH SAID PACKER, SAID FIRST VALVE MEANS AND SAID ONE PIPE STRING, AND ANOTHER POSITION WHICH PREVENTS FLUID COMMUNICATION BETWEEN SAID FORMATION AND THE EARTH''S SURFACE THROUGH SAID PACKER AND SAID FIRST VALVE MEANS BUT WHICH ESTABLISHES A SECOND FLOW PATH BETWEEN THE EARTH''S SURFACE AND THE SPACE SURROUNDING SAID PIPE STRINGS ABOVE SAID PACKER THROUGH SAID FIRST VALVE MEANS AND SAID ONE PIPE STRING; MEANS LOWERABLE THROUGH SAID ONE PIPE STRING FOR MOVING SAID FIRST VALVE MEANS FROM ITS ONE POSITION TO ITS OTHER POSITION AND VICE VERSA; AT LEAST ONE SECOND VALVE MEANS ARRANGED IN SAID OTHER PIPE STRING ABOVE SAID FIRST VALVE MEANS AND MOVABLE BETWEEN ONE POSITION WHICH PREVENTS FLUID COMMUNICATION BETWEEN THE INTERIOR OF SAID OTHER PIPE STRING AND THE SPACE SURROUNDING IT AND ANOTHER POSITION WHICH ESTABLISHES A THIRD FLOW PATH BETWEEN SAID FORMATION AND THE SPACE SURROUNDING SAID PIPE STRINGS ABOVE SAID PACKER THROUGH SAID OTHER PIPE STRING AND SAID SECOND VALVE MEANS; AND MEAN LOWERABLE THROUGH SAID OTHER PIPE STRING TO A POSITION ADJACENT SAID FORMATION FOR MOVING SAID SECOND VALVE MEANS FROM ITS ONE TO ITS OTHER POSITION AND VICE VERSA, THE STEPS COMPRISING: POSITIONING SAID FIRST VALVE MEANS IN ITS POSITION; INJECTING AIR FROM THE EARTH''S SURFACE INTO SAID FORMATION ALONG SAID FIRST FLOW PATH TO INITIATE AND MAINTAIN IN SITU COMBUSTION FOR A SELECTED TIME; TERMINATING SAID INJECTION OF AIR AFTER SAID SELECTED TIME TO COMPLETE THE COMBUSTION PHASE; PRODUCING OIL FROM SAID FORMATION TO THE EARTH''S SURFACE ALONG SAID FIRST FLOW PATH UNTIL PRODUCTION CEASES; POSITIONING SAID FIRST VALVE MEANS IN ITS OTHER POSITION TO ESTABLISH SAID SECOND FLOW PATH; POSITIONING SAID SECOND VALVE MEANS IN ITS OTHER POSITION TO ESTABLISH SAID THIRD FLOW PATH; AND PUMPING OIL TO THE EARTH''S SURFACE FROM ADJACENT SAID FIRST VALVE MEANS, SAID HYDROCARBONS PRODUCED FROM SAID FORMATION FLOWING UPWARDLY THEREFROM THROUGH SAID THIRD FLOW PATH INTO THE SPACE SURROUNDING SAID PIPE STRINGS ABOVE SAID PACKER WHERE GAS SEPARATES FROM OIL, THE GAS FLOWING UPWARDLY THROUGH THE ANNULUS BETWEEN SAID OTHER PIPE STRING AND THE WELL BORE WALL TO THE EARTH''S SURFACE AND THE OIL FLOWING FROM SAID THIRD FLOW PATH INTO SAID SECOND FLOW PATH AND, THENCE, UPWARDLY TO THE EARTH''S SURFACE. 